Aug. 19, 1922] THE BACTERIOPHAGE. [muo'.cal Jouknai. 



bacterial, vegetable, or animal, according to its source, and which possesses the 

 powei either of directly increasing in quantity or of stimulating the cell to 

 produce more pathological enzyme. On the other hand, it is conceivable that 

 if this lytic agent be a pathological enzyme, it might bear the same relation 

 to the normal enzyme that the cancer cell does to the normal cell. These 

 possibilities may sound very improbable, but at the same time some such 

 explanation would account for the extremely specific nature of many of the 

 ultramicroscopic viruses, and it would certainly explain the absence of 

 visibility and of growth on artificial media. After all, excluding such organisms 

 as the lepto-spirillum of yellow fever, which probably belongs to an entirely 

 different group, there are fundamental differences between the smallest micro- 

 organisms known and the various ultramicroscopic viruses. 



Cultivations of the minutest micro-organisms known show all the charac- 

 teristics of ordinary bacteria. If these are obtained from the soil many of them 

 grow well. On the other hand, if ultramicroscopic viruses are simply more 

 minute members of the group of bacteria, there must be thousands of wild 

 varieties in the soil, and yet no one has succeeded in obtaining a definite 

 growth of a single variety on any solid medium. Minuteness of size might 

 account for their being invisible, but it will not explain the absence of visible 

 growth on artificial solid media. It is true that certain workers at one time 

 claimed to have obtained growths of pathogenic varieties in Noguchi's medium, 

 but in the absence of definite confirmation these experiments need not be 

 considered here. 



Professor Bordet and Dr. Ciuca have carried out some most important 

 experiments with the dysentery-typhoid-coli group of bacilli on the specificity 

 of the lytic material, and have obtained results which indicate not only that the 

 lytic agent can be made to break down allied bacilli, but also that certain 

 resisting and otherwise changed strains can be obtained. As I have already 

 mentioned, my micrococcus lysin had little effect on Staphylococcus aureus; 

 but I did not carry out many experiments of this nature after obtaining the 

 apparent spontaneous production of the lytic agent in my pure cultures of 

 micrococci, as this result appeared to me to make it difficult to draw definite 

 conclusions from such experiments. Many other workers, but particularly Dr. 

 d'Herelle and Dr. Andre Gratia, have also carried out important experiments 

 in this branch of the subject, but I must leave other speakers to deal with it, 

 as it is impossible in the space at my disposal to do justice to their work. 



There is, however, another aspect of the subject which I should like to 

 mention. As is well known, in pure cultures of such bacilli as dysentery, 

 typhoid, and coli, one sometimes meets with forms which are considerably 

 larger and longer than the average bacillus, and these may be found in patho- 

 logical material containing these bacilli, being not uncommon in urine in cases 

 of cvstitis. Hort and others have described these large forms in considerable 

 detail. 



In certain experiments dealing with the lytic material I observed these long 



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